Storage control device to backup data stored in virtual volume

ABSTRACT

A storage control device uses write management information that manages locations of the occurrence of writing in one or more first storage devices in order to specify one or more locations where writing has occurred, and backs up one or more data elements stored in one or more specified locations to a second storage device. In order to perform a restore operation, write management information at the time of a backup is stored, and data elements stored in the second storage device are restored to one or more locations specified from the write management information at that time of backup, or to one or more new locations specified from new write management information indicating one or more new locations corresponding to the one or more locations.

CROSS-REFERENCE TO PRIOR APPLICATION

This application relates to and claims the benefit of priority fromJapanese Patent Application No. 2007-13384, filed on Jan. 24, 2007, theentire disclosure of which is incorporated herein by reference.

BACKGROUND

The present invention relates to technology for data backup.

Storage systems can provide storage areas to host computers in unitscalled virtual volumes. In general, the storage capacity of a virtualvolume is fixed; but there exists technology to automatically expand thestorage capacity of a virtual volume, by allocating to the virtualvolume a partial area of a physical resource (hereafter called a“segment”), in response to an access request from a host computer, inorder to increase the efficiency of storage area utilization. Forexample, a disclosure of Japanese Patent Laid-open No. 2003-15915 isrelated to such technology.

A virtual volume is a virtual logical volume. A storage system can showto a host computer (specifically, for example, to an applicationexecuted by the host computer) a virtual storage capacity (hereaftercalled a “virtual capacity”) different from the total storage capacityof one or more segments actually allocated to the virtual volume(hereafter called the “actual capacity”). By allocating a segment to avirtual volume, the actual capacity of the virtual volume increases by(is expanded by) the storage capacity of the segment. Consequently, avirtual volume can also be called a “capacity expansion volume”. Or,because a virtual volume is a logical volume which can be provided using“thin provisioning” technology, a virtual volume can also be called a“thin provisioning volume”.

For example, a method exists in which a host computer is connected todisk storage and a tape library apparatus by a communication networkcalled a Storage Area Network (SAN), and data stored in the disk storageis backed up in volume units to the tape library apparatus by a serverfor backup processing (hereafter called a “backup server”). In thiscase, the backup server reads data from logical volumes of the diskstorage, and stores the read-out data to the tape library apparatus.

When a logical volume for backup is a virtual volume as described above,the virtual volume appears to the backup server to be a virtual volumewith a virtual capacity amount different from the actual capacity, andso at the time of backup, reading and writing of the virtual capacityamount is performed. In general, the actual capacity is smaller than thevirtual capacity. For this reason, reading and writing of the virtualcapacity amount includes unnecessary reading and writing.

Further, when for example backed-up data is restored, in a processopposite that of the backup process, and more specifically, when data isrestored to a logical volume within the disk storage from the tapelibrary apparatus via the backup server, writing occurs to the virtualvolume which is the restore destination in the virtual capacity amount,and so a larger actual capacity is required than at the time of backup.

The above problems can similarly occur when the backup source is astorage device of a type different from the disk storage, and/or whenthe backup destination is a storage device of a type different from thetape library apparatus.

SUMMARY

Hence an object of this invention is to prevent the occurrence ofunnecessary reading and writing in the backup of a virtual volume.

Another object of the invention is to prevent the need for a largeractual capacity during restoring of a virtual volume than at the time ofbackup.

Other objects of the invention will become clear from the followingexplanation.

In a backup operation, a storage control device references writemanagement information, which is information to manage the location ofoccurrence of writing in one or more first storage devices related to aplurality of segments, in order to specify one or more locations of theoccurrence of writing in the one or more first storage devices, andbacks up the one or more data elements stored in the specified one ormore locations to a second storage device.

In order to perform a restore operation, the storage control devicestores write management information at the time of a backup. In arestore operation, the storage control device acquires the writemanagement information stored at the time of the backup, and restores,to one or more locations specified from the write managementinformation, or to one or more new locations specified from new writemanagement information representing one or more new locationscorresponding to the one or more locations, one or more data elementsstored in one or more locations among the plurality of data elementsstored in the second storage device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of the configuration of a computer system in oneembodiment of the invention;

FIG. 2 shows an example of the configuration of a disk array controllerof a storage virtualization apparatus;

FIG. 3 shows an example of the configuration of the virtual disk arraycontroller of a virtual disk library apparatus;

FIG. 4 shows an example of the configuration of a segment managementtable;

FIG. 5 shows an example of the configuration of a physical/logicalmanagement table;

FIG. 6 shows an example of the configuration of an external diskcorrespondence table;

FIG. 7 shows an example of the processing flow for backup processing ina first embodiment of the invention;

FIG. 8 shows a portion of an example of the processing flow for restoreprocessing in the first embodiment of the invention;

FIG. 9 shows the remaining portion of an example of the processing flowfor restore processing in the first embodiment of the invention;

FIG. 10 shows an example of the configuration of a physical/logicalmanagement table with restore destination information appended;

FIG. 11 shows an example of the configuration of a computer system in asecond embodiment of the invention;

FIG. 12 shows an example of the configuration of the virtual disk arraycontroller of a virtual disk library apparatus in the second embodimentof the invention;

FIG. 13 shows an example of the configuration of a disk;

FIG. 14 shows an example of the configuration of a differentialmanagement table;

FIG. 15 shows an example of a differential bitmap;

FIG. 16 shows an example of the processing flow for backup processing inthe second embodiment of the invention;

FIG. 17 shows an example of the flow of processing for restoreprocessing in the second embodiment of the invention;

FIG. 18 shows an example of the configuration of a computer system in athird embodiment of the invention;

FIG. 19 shows an example of the configuration of the virtual disk arraycontroller of the virtual disk library apparatus in the third embodimentof the invention;

FIG. 20 shows an example of the configuration of a segment managementtable in the third embodiment of the invention;

FIG. 21 shows an example of the configuration of a physical/logicalmanagement table in the third embodiment of the invention;

FIG. 22 shows an example of the processing flow for backup processing inthe third embodiment of the invention;

FIG. 23 shows an example of the processing flow for restore processingin the third embodiment of the invention; and,

FIG. 24 shows an example of the processing flow for restore processingin a fourth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention are explained in summary below.

A storage control device is comprised by a virtualization system, whichallocates unallocated segments, among a plurality of segments, accordingto a write operation to a virtual volume which is a virtual logicalvolume provided to a higher-level device, and writes data elements tothe allocated segments according to the write operation. This storagecontrol device may for example be a virtual disk library apparatus,described below, but is not limited thereto, and other types of devicemay be provided instead.

The storage control device comprises one or more first storage devicesrelated to a plurality of segments, a second storage device, and abackup control portion. The backup control portion uses write managementinformation, which is information used to manage the locations of writeoperations in the one or more first storage devices, to identify one ormore locations in which writing has occurred in one or more firststorage devices, and backs up one or more data elements stored in theidentified one or more locations to the second storage device.

Here, “one or more first storage devices related to a plurality ofsegments” is one or more first storage devices, comprising segments orstorage areas corresponding to segments. In this case, when writing of adata element to a certain segment occurs, writing of the data element tothe certain segment itself or to a storage area corresponding to thecertain segment occurs. A specific example of one or more first storagedevices, in the cases of the first through fourth embodiments describedbelow, may be disks within a virtual disk library apparatus.

As each of the one or more first storage devices, a random access-typestorage device can be adopted. Such a storage device may for example bea hard disk drive, DVD drive, or other disk-type storage device, or maybe flash memory or some similar memory device. As the second storagedevice, a sequential access-type storage device can be adopted. Such astorage device may for example be a device which uses tape media.However, these devices are not limited to such examples, and for examplea sequential access-type storage device may be used as a first storagedevice, and a random access-type storage device may be used as a secondstorage device.

A storage control device can further comprise a storage portion and arestore control portion. The storage portion can store the writemanagement information at the time of a backup. The restore controlportion can read the write management information stored at the time ofa backup, and can restore one or more data elements stored in the secondstorage device to one or more locations identified from the read-outwrite management information, or to one or more new locations identifiedfrom new write management information representing one or more newlocations corresponding to the above one or more locations. The newwrite management information is information which has been generatedbased on read-out write management information.

The storage portion may store the write management information for abackup in the second storage device, or may store the information inanother storage device (for example, in memory within the storagecontrol device).

A storage control device can be connected to a virtualization apparatus.This virtualization apparatus can comprise storage resources, a writecontrol portion, and a write management information transmissionportion. Storage resources can store allocation management information,which is information representing which segment, among the plurality ofsegments comprised by one or more virtual first storage devices, hasbeen allocated to the virtual volume based on one or more first storagedevices, and correspondence management information, representing thecorrespondence between each of the plurality of segments and physicalareas in the one or more first storage devices. The write controlportion can receive a first write request for write data to be writtento the virtual volume from a higher-level device; in response to thefirst write request, select one or more unallocated segments from amongthe plurality of segments based on the allocation managementinformation; allocate the selected unallocated one or more segments tothe virtual volume; update the allocation management information withinformation indicating that one or more segments have been allocated tothe virtual volume; use the correspondence management information toupdate the one or more physical areas corresponding to the allocated oneor more segments; and transmit to the storage control device a secondwrite request, for writing of the write data to the identified one ormore physical areas. The write management information transmissionportion can transmit the write management information, comprisingallocation management information and correspondence managementinformation, to the storage control device.

A virtualization apparatus may further comprise a segment reallocationportion. The restore control portion can read out write managementinformation for a backup, and can transmit the read-out write managementinformation to the virtualization apparatus. The segment reallocationportion of the virtualization apparatus can associate one or more newsegments with one or more segments identified by the storage controldevice from the write management information, generate new writemanagement information representing the one or more new physical areascorresponding to the one or more new segments based on the writemanagement information, and transmit the generated new write managementinformation to the storage control device. The restore control portionof the storage control device can restore, to the one or more newphysical areas identified by the virtualization apparatus from the newwrite management information, one or more data elements stored in thesecond storage device.

The virtualization apparatus need not comprise a write managementinformation transmission portion. Further, the restore control portionof the storage control device need not comprise a function to transmitwrite management information to the virtualization apparatus. In thiscase, for example, the storage control device can comprise a writeexecution portion. The write execution portion can write the write dataaccording to a second write request from the virtualization apparatus toone or more physical areas in one or more first storage devicesaccording to the second write request, and can update the writemanagement information with information indicating the occurrence ofwriting to the one or more physical areas. The backup control portioncan use the updated write management information to identify one or morephysical areas in the one or more first storage devices in which writinghas occurred, and can back up the one or more data elements stored inthe identified one or more physical areas to the second storage device.The virtualization apparatus may further comprise an allocationmanagement information storage portion, which stores allocationmanagement information at the time of a backup. The restore controlportion can restore one or more data elements stored in the secondstorage device to one or more physical areas identified from the writemanagement information for a backup, and the allocation managementinformation storage portion can restore the allocation managementinformation at the time of backup of one or more restored data elementsto the storage resources. The allocation management information storageportion may store allocation management information for a backup in atleast one among the one or more storage devices, or may store theinformation in another storage device (for example, memory in thevirtualization apparatus, or memory in the storage control device).

In a case in which a plurality of elements, in the amount of the virtualcapacity amount, are backed up to the second storage device, the restorecontrol portion may identify, from among the plurality of data elementsstored in the second storage device, one or more data elements stored inthe one or more locations identified from the write control informationfor the time of backup, and may restore only the one or more identifieddata elements to the one or more first storage devices.

Each of the portions described above can be constructed by means ofhardware, a computer program, or a combination thereof (for example,with a portion realized by a computer program, and the remainderrealized in hardware). A computer program is read and executed by aprescribed processor. In the event of information processing performedwhen a computer program is read by a processor, storage space existingin memory and other hardware resources may be used as appropriate. Acomputer program may also be installed onto a computer from a CD-ROM orother recording media, or may be downloaded to a computer over acommunication network.

Below, a number of embodiments of the invention are explained in detail,referring to the drawings. In the following explanation, the data storedin one segment, or in the physical area corresponding to the segment, iscalled a “data element”.

First Embodiment

FIG. 1 shows an example of the configuration of a computer system in afirst embodiment of the invention.

The host computer 100, storage virtualization apparatus 110, and virtualdisk library apparatus 120 are connected using fiber channel 140 via aswitch 130, and exchange data, processing requests and similar. The hostcomputer 100 storage virtualization apparatus 110 and virtual disklibrary apparatus 120 may be connected via a LAN (Local Area Network) orother communication network, or may be connected via dedicated circuitsor similar.

The host computer 100 comprises a CPU 104 and memory 103. In the memory103 are stored, as a plurality of computer programs, for example, anapplication 101 and a backup/restore control instruction program 102.These computer programs are executed by the CPU 104. Below, when acomputer program is the subject of a sentence, processing is inactuality performed by the CPU which executes the program. Theapplication 101 writes data to a logical volume (for example, a virtualvolume) provided by the storage virtualization apparatus 110, and readsdata from the logical volume. The backup/restore control instructionprogram 102 issues various commands, such as backup initiationinstructions and restore initiation instructions.

The storage virtualization apparatus 110 comprises a disk arraycontroller 111; one or more (for example, two) virtual volumes 112; oneor more (for example, two) disks 113; one or more (for example, two)disk devices 116; and one or more (for example, two) external disks 114.The disk devices 116 may be disk-type storage devices, such as hard diskdrives, DVD drives or similar, but may some other type of storage device(such as a flash memory device) as well. The disks 113 are logicalvolumes, formed based on storage space of at least one disk device 116among the one or more disk devices 116. The external disks 114 arevirtual logical volumes, formed based on storage space of at least onedisk device 126 (at least one disk device 126 in a virtual disk libraryapparatus 120) external to the storage virtualization apparatus 110. Theexternal disks 114 may be provided by employing for example thetechnology disclosed in Japanese Patent Laid-open No. 2005-107645 (U.S.patent application Ser. No. 10/769,805, U.S. patent application Ser. No.11/471,556), or may be associated one-to-one with an external disk(logical volume) 122. Segments of one or more disks 113 are allocated toa virtual volume 112 a. Segments of one or more external disks 114 areallocated to a virtual volume 112 b. Data written to segments of anexternal disk 114 correspond to these segments. Writing is to thephysical area comprised by the disks 122.

The virtual disk drive library apparatus 120 comprises a virtual diskarray controller 121, one or more disks 122, one or more disk devices126, and a tape library apparatus 123. The disk devices 126 aredisk-type storage devices; but another type of storage device (such as aflash memory device) may be used. The tape library apparatus 123comprises one or more tapes 126, a robot 124 which moves tapes 126, anda tape drive 125 which writes data to and reads data from tapes 126.

FIG. 2 shows an example of the configuration of a disk array controller111.

The disk array controller 111 comprises a computer IF portion 200, whichis the interface with the host computer 100; a disk control program 211;local memory (hereafter called control memory) 210, which stores avirtual volume correspondence table 212 and external disk correspondencetable 213; a processor (for example, a CPU; hereafter called a controlprocessor) 220, which executes the disk control program 211; cachememory 230, which temporarily stores data; a disk IF portion 240, whichis the interface with disks 113; and, an external IF portion 250, whichis the interface with the virtual disk library apparatus 120.

The disk control program 211 has functions to show virtual volumes 112 aand 112 b to the host (for example, the application 101) using thevirtual volume correspondence table 212. Further, the disk controlprogram 211 has functions to use the external disk correspondence table213 to handle a disk 122 of the virtual disk library apparatus 120,externally connected to the storage virtualization apparatus 110, as anexternal disk 114. Unused segments among the plurality of segmentscomprised by the disk 113 are allocated to a plurality of address rangesof the virtual volume 112 a in accordance with the access (for example,by writing) to the address ranges. Hence each of the actual areas of thevirtual volume 112 a can be regarded as a segment on the disk 113allocated to this virtual volume 112 a. On the other hand, unusedsegments among the plurality of segments comprised by the external disk114 are allocated to each of a plurality of address ranges of thevirtual volume 112 b, according to accessing of (for example, writingto) the address ranges. The allocated segments correspond to theplurality of physical areas (storage areas) comprised by the disk 112.Hence each of the actual areas of the virtual volume 112 b may be asegment of the external disk 114 allocated to this virtual volume 112 b,or may be a physical area in the disk 122 corresponding to a segment. Asthe storage capacities of the virtual volumes 112 a and 112 b, virtualcapacities (storage capacities equal to or greater than the actualcapacities) different from the actual capacities (the total storagecapacity of the one or more allocated segments) are provided to thehost. The disk control program 211 further has functions for managingthe disks 113 and external disks 114 of the storage virtualizationapparatus 110.

FIG. 3 shows an example of the configuration of a virtual disk arraycontroller 121.

The virtual disk array controller 121 comprises an FE/IF portion 300,which is the interface to the storage virtualization apparatus 110; adisk control program 311; a tape library control program 312; localmemory (hereafter called control memory) 310, which stores a backupcontrol program 313 and restore control program 314; a processor (forexample, a CPU; hereafter called a control processor) 320, whichexecutes the disk control program 311, the tape library control program312, backup control program 313, and restore control program 314; cachememory 330, which temporarily stores data; disk IF portion 340, which isthe interface with disks 122; and tape IF 350, which is the interfacewith the tape library apparatus 123.

The disk control program 311 has functions to manage and control disks122 of the virtual disk library apparatus 120. Specifically, forexample, upon receiving a first write request for the virtual volume 112b from the host computer 100, the disk control program 211 of thestorage virtualization apparatus 110 identifies an unallocated segmentin the external disk 114 from the segment management table 400,identifies the disk 122 with the physical area corresponding to theidentified segment from the external disk correspondence table 213, andtransfers to the virtual disk library apparatus 120 a second writerequest, specifying the identified disk 122 and the addresscorresponding to the identified segment (the physical area address). Inresponse to this second write request, the disk control program 311writes the data element of the data according to the second writerequest to the physical area corresponding to the address specified bythe second write request.

The tape library control program 312 has functions for managing andcontrolling the tape library apparatus 123 of the virtual disk library120. Specifically, upon backup processing and restore processing of thevirtual volumes 112 a and 112 b, for example, the backup control program313 and restore control program 314 are executed; but in this backupprocessing and restore processing, data writing to the tape 126, anddata reading from the tape 126, are performed by appropriately callingand executing the tape library control program 312 from the backupcontrol program 313 or restore control program 314. Below, backupprocessing is explained referring to FIG. 7, and restore processing isexplained referring to FIG. 8 and FIG. 9; but in order to avoid a prolixexplanation, here an explanation relating to calling of the tape librarycontrol program 312 is omitted.

The backup control program 313 has a function (hereafter called a backupfunction) to act in cooperation with the disk control program 311 andtape library control program 312 to copy data on the disk 122 to thetape 126. The backup control program 313 further has a function tocommunicate with the storage virtualization apparatus 110, and toperform a backup while referencing the virtual volume correspondencetable 212 and external disk correspondence table 213, so that only theactual areas of the virtual volume 112 b. The backup control program 313further has a function to communicate with the storage virtualizationapparatus 110, and to copy a portion of or all of the virtual volumecorrespondence table 212 and external disk correspondence table 213 totape 126.

The restore control program 314 has a function (hereafter called arestore function) to act in cooperation with the disk control program311 and tape library control program 312, to copy data on the tape 126to the disk 122. Further, the restore control program 314 has a functionfor communicating with the storage virtualization apparatus 110 andtransmitting the virtual volume correspondence table 212 and externaldisk correspondence table 213, stored on the table 126, to the diskcontrol program 211. The disk control program 211 has a function toreference the virtual volume correspondence table 212 and external diskcorrespondence table 213 received from the restore control program 314,and create a virtual volume 112 b to serve as the restore destination.The disk control program 211 has a function to transmit the virtualvolume correspondence table 212 and external disk correspondence table213, which serve as restore destination information, to the restorecontrol program 314. The restore control program 314 has a function toperform a restore operation while referencing the virtual volumecorrespondence table 212 and external disk correspondence table 213received from the disk control program 211.

The above-described virtual volume correspondence table 212 can comprisethe segment management table 400 of FIG. 4 and the physical/logicalmanagement table 500 of FIG. 5.

FIG. 4 shows an example of the configuration of a segment managementtable 400.

A segment management table 400 is used to manage segments allocated asactual areas to the virtual volumes 112 a, 112 b. Segment managementtables 400 include a segment management table for disks 113, and asegment management table for external disks 114. FIG. 4 shows arepresentative example of a segment management table for external disks114 (a segment management table for disks 113 is omitted).

In a segment management table 400 for an external disk 114 are stored,for each external disk 114, the external disk ID 410, Segment Number(hereafter either “SN” or “segment number”) 420, LBA (START) 430, Size440, and In-use 450. The external disk ID 410 is a unique identificationnumber for an external disk 114 (for example, a number determined by thedisk control program 211). A segment is the minimum unit of storage areainto which each disk 113 and external disk 114 is divided to be managedby the disk control program 211, and the SN 420 is a uniqueidentification number used to manage segments in the disk controlprogram 211. The LBA (START) 430 stipulates the physical position fromwhich the segment starts within an external disk 114 with an externaldisk ID 410. Size 440 indicates the size of the storage area startingfrom LBA (START) 430 within the external disk 114. In-use 450 indicatesthe state of use of the segment, employing two values to indicatewhether the segment is or is not being used by the disk control program211. When the segment is being used, a value of 1 is stored, and whennot in use a value of 0 is stored, to indicate the state of use.

FIG. 5 shows an example of the configuration of a physical/logicalmanagement table 500.

A physical/logical management table 500 is used for physical/logicaladdress management between a virtual volume 112 provided by the diskcontrol program 211 and the disk 113 or external disk 114 in which datais stored. The physical/logical management table 500 stores, for eachvirtual volume 112, the LUN 510, capacity 520, SN 530, LUN LBA (START)540, and LUN LBA (END) 550. The LUN 510 is the logical unit number, andis a unique number for a logical volume provided to the host computer100 by the disk control program 211. The virtual volume 112 is providedto the host computer 100 as a logical volume. The capacity 520 is thecapacity of the virtual logical volume (virtual capacity) provided tothe host computer 100. The SN 530 is a unique number for a storage areamanaged by the disk control program 211. The LUN LBA (START) 540indicates the LBA starting position in the address range which is thesegment allocation destination (virtual volume address range). The LUNLBA (END) 550 indicates the LBA ending position in the address rangewhich is the segment allocation destination (virtual volume addressrange).

The disk control program 211 monitors LBAs within individual I/Orequests for logical volume access from the host computer 100, and whennecessary performs processing to increase or decrease the actual area ofthe logical volume. Specifically, within for example a virtual volumeLUN0 (510), when there is a write request specifying an address in theaddress range 0 to 999, for example, a segment SN1 (420) is allocated tothe address range 0 to 999. In this case, SN1 is stored in thephysical/logical management table 500 as the SN (530), and the In-use(450) value corresponding to SN1 (420) is set to 1. On the other hand,in for example virtual volume LUN0 (510), when a segment SN1 (530) isreleased from the address range 0 to 999, SN1 (420) is deleted from thephysical/logical management table 500, and the In-use (450) valuecorresponding to SN1 (420) is set to 0.

FIG. 6 shows an example of the configuration of an external diskcorrespondence table 213.

An external disk correspondence table 213 is provided to manage thecorrespondence between external disks 114 and disks of other devices(for example, disks 122). In an external disk correspondence table 213are stored, for each external disk 114, the external disk ID 610, deviceID 620, and disk ID 630. The external disk ID 610 is a uniqueidentification number for the external disk 114, determined by the diskcontrol program 211. The device ID 620 is a unique identification numberfor the device externally connected to the storage virtualizationapparatus 110 (for example, a virtual disk library apparatus 120). Thedisk ID 630 is a unique identifying number for a disk within the deviceidentified by the device ID 620. For example, an external disk 114 withan external disk ID 0 (611) corresponds to a disk (for example, a disk122) with disk ID 100 (631) of a device ID 1 (621). In FIG. 6, theexternal disks and disks are in a one-to-one correspondence; but asingle external disk may correspond to a plurality of disks, or aplurality of external disks may correspond to a single disk.

FIG. 7 shows the processing flow of backup processing.

In step 7010, the backup/restore control instruction program 102 of thehost computer 100 transmits a backup initiation instruction for a LU tobe backed up to the virtual disk library apparatus 120, and the virtualdisk library apparatus 120 receives this backup initiation instruction.For example, in the backup initiation instruction, the LUN of a virtualvolume 112 a or 112 b which is to be backed up (the backup source), anda tape 126 which is the backup destination, are specified. The tape 126which is the backup destination need not be specified; in this case, thecorrespondence relation between an arbitrarily selected table 126 (anunused tape 126 not yet used as a backup destination for data) and theLUN which is the backup source may be managed by storing in a table, notshown, or by other means. Moreover, a plurality of virtual volumes 112 aor 112 b may be specified together for backup. In this processing flow,the virtual volume 112 b may be the LU for back up. Or, in place of atape 126, the LUN of a tape LU may be specified. A tape LU is a logicalunit corresponding to all of or a portion of the storage space of one ormore tapes 126.

In step 7020, in response to the above backup initiation instruction,the backup control program 313 of the virtual disk library apparatus 120notifies the storage virtualization apparatus 110 of the initiation ofbackup of the LU for backup 112 b (virtual volume 112 b).

In step 7030, the storage virtualization apparatus 110 receives thebackup initiation notification for the LU for backup 112 b.

In step 7040, in response to the backup initiation notification, thedisk control program 211 of the storage virtualization apparatus 110prohibits writing to the LU for backup 112 b from a higher-level device(for example, from the host computer 100). Specifically, for example,even when a write request for the LU for backup 112 b is received fromthe host computer 100, the disk control program 211 returns a busyresponse to the write request or does not respond at all, so that datais not written to the LU for backup 112 b according to the writerequest. The disk control program 211 can notify the virtual disklibrary apparatus 120 of the write-prohibited state of the LU for backup112 b.

In step 7050, for example in response to the notification of thewrite-prohibited state from the storage virtualization apparatus 110,the backup control program 313 of the virtual disk library apparatus 120is executed. In step 7050, the backup control program 313 requests thevirtual volume correspondence table 212 and external disk correspondencetable 213 relating to the LU for backup 112 b from the storagevirtualization apparatus 110. A request may be issued for all of thevirtual volume correspondence tables 212 and external diskcorrespondence tables 213.

In step 7060, the storage virtualization apparatus 110 receives therequest from the virtual disk library apparatus 120.

In step 7070, in response to this request, the disk control program 211of the storage virtualization apparatus 110 transmits to the virtualdisk library apparatus 120 the virtual volume correspondence table 212and external disk correspondence table 213 requested by the virtual disklibrary apparatus 120.

In step 7080, the virtual disk library apparatus 120 receives thevirtual volume correspondence table 212 and external disk correspondencetable 213 transmitted from the storage virtualization apparatus 110.

In step 7090, the backup control program 313 of the virtual disk libraryapparatus 120 copies, to the tape 126 serving as the backup destination(the tape 126 specified by the backup initiation instruction), thevirtual volume correspondence table 212 and external disk correspondencetable 213 (the virtual volume correspondence table 212 and external diskcorrespondence table 213 transmitted from the storage virtualizationapparatus 110) which are necessary when restoring the LU for backup 112b. The virtual volume correspondence table 212 and external diskcorrespondence table 213 are for example written from the beginning ofthe tape 126 serving as the backup destination. In place of writing fromthe beginning, writing may be at a prescribed position or at anarbitrary position on the tape 126 serving as the backup destination, ormay be in a prescribed storage area within the tape library apparatus123. The locations of writing of virtual volume correspondence tables212 and external disk correspondence tables 213 corresponding todifferent LUs for backup are stored in a table, not shown, and whenrestoring a LU for backup, this table is referenced to identify thelocations in which the virtual volume correspondence table 212 andexternal disk correspondence table 213 corresponding to the LU forbackup are stored, so that the virtual volume correspondence table 212and external disk correspondence table 213 may be read from theidentified positions.

In step 7100, the backup control program 313 references the virtualvolume correspondence table 212 and external disk correspondence table213, identifies each of the physical areas comprised by the disk 122equivalent to each of the actual areas of the LU for backup 112 b, andcopies each of the data elements stored in these physical areas from thephysical areas to the tape 126 which is the backup destination. Forexample, in the case in which the LU for backup 112 b is the LU LUN0 ofFIG. 5, the physical areas corresponding to segment number 1 (521),segment number 2 (522), and segment number 3 (523) are backup sources.From FIG. 4 and FIG. 6, the segment corresponding to segment number 1(521) of size 1000 (441) starting from LBA (START) 0 (431) within thedisk 122 with disk ID 100 (631) in the device with ID 1 (621); thisphysical area is the actual area. Similarly, segment number 2 (522) is aphysical area of size 1000 (442) starting from LBA (START) 1000 (432)within a disk 122 with disk ID 100 (631) of device ID 1 (621), andsegment number 3 (523) is a physical area of size 1000 (443) startingfrom LBA (START) 2000 (433) within a disk 122 with disk ID 100 (631) ofdevice ID 1 (621). In the backup of LU LUN0, copying of data elements isperformed with these physical areas as the backup source and a tape 126as the backup destination. As the order of copying, the order of thesegment numbers (for example, for LUN0, in the order segment 1, 2, 3)stored in the physical/logical management table 500 (see FIG. 5) can beused. In place of this, copying may be performed in any other regularorder, or copying may be in no regular order. When copying in no regularorder, management may be performed by for example storing in a table,not shown, to which positions on the tape 126 which is the backupdestination the data elements of physical areas corresponding to whichsegment numbers have been copied.

In step 7110, after completion of backup of the LU for backup 112 b, thebackup control program 313 notifies the storage virtualization apparatus110 of the completion of backup of the LU for backup 112 b.

In step 7120, the storage virtualization apparatus 110 receivesnotification of the completion of backup of the LU for backup 112 b.

In step 7130, the disk control program 211 of the storage virtualizationapparatus 110 permits writing to the LU for backup 112 b (in otherwords, cancels the write prohibition state).

In step 7140, the virtual disk library apparatus 120 notifies thebackup/restore control instruction program 102 of the host computer 100of the completion of backup of the LU for backup 112 b.

Through the above flow of processing, backup processing is performed. Inthis backup processing, when for example an unused area remains on thetape 126 which is the backup destination, in the next and subsequentbackup processing, the virtual volume correspondence table 212 orsimilar may be stored from the beginning of this unused area, or, acompletely unused tape 126 (a tape 126 on which data can be written fromthe tape beginning) may be selected, and the virtual volumecorrespondence table 212 and similar stored onto this tape 126.

The combination of FIG. 8 and FIG. 9 show the processing flow of restoreprocessing.

In step 8010, the backup/restore control instruction program 102 of thehost computer 100 transmits a restore initiation instruction for a LUfor restoring to the virtual disk library apparatus 120, and theinstruction is received by the virtual disk library apparatus 120. Forexample, in the restore initiation instruction, the tape 126 to serve asthe restore source and the LUN of the virtual volume 112 for restoring(the LUN of the LU for restoring) may be specified. The LU which is therestore destination may be the LU for restoring (in other words, thebacked-up LU), or may be a LU different from the LU for restoring.Specifically, when for example the LUN of the backed-up LU is 0, and thebacked-up LU is to be restored, the LUN of the LU for restoring is also0, but the LU which is the restore destination may be the LU forrestoring (the LU LUN0), or may be a different LU. Further, the tape 126serving as the restore source need not be specified; in this case, forexample, the tape 126 on which is stored the LU specified for restoringis identified from among above-described tapes, not shown, and theidentified tape 126 may serve as the restore source. Further, aplurality of LUs may together serve as the LU for restoring. In thisprocessing flow, a virtual volume 112 b is the LU for restoring, andalso the restore destination. In place of a tape 126, the LUN of a tapeLU may be specified. A tape LU is a logical unit corresponding to all ora portion of the storage space of one or more tapes 126.

In step 8020, for example in response to a restore initiationinstruction, the restore control program 314 of the virtual disk libraryapparatus 120 notifies the storage virtualization apparatus 110 of theinitiation of a restore operation for the LU for restoring 112 b.

In step 8030, the storage virtualization apparatus 110 receives therestore initiation notification for the LU for restoring 112 b.

In step 8040, in response for example to the above restore initiationnotification, the disk control program 211 of the storage virtualizationapparatus 110 prohibits writing to the LU for restoring 112 b from ahigher-level device (for example, from the host computer 100). Thisprocessing is for example effectively similar to that of step 7040.

In step 8050, for example in response to notification of thewrite-prohibited state from the storage virtualization apparatus 110,the restore control program 314 of the virtual disk library apparatus120 reads the virtual volume correspondence table 212 and external diskcorrespondence table 213 from the tape 126 which is the restore source.

In step 8060, the restore control program 314 transmits to the storagevirtualization apparatus 110 the virtual volume correspondence table 212and external disk correspondence table 213 read from the tape 126.

In step 8070, the disk control program 211 of the storage virtualizationapparatus 110 receives the virtual volume correspondence table 212 andexternal disk correspondence table 213 transmitted from the virtual disklibrary apparatus 120.

In step 8080, the disk control program 211 resets allocation of actualareas of the LU for restoring 112 b. Specifically, for example, the diskcontrol program 211 resets the SN (530) of the LU for restoring 112 b inthe physical/logical management table 500, and changes the In-use (450)value in the segment management table 400 for the reset segment numberto 0 (unused).

In step 8090, the disk control program 211 references the receivedvirtual volume correspondence table 212 and external disk correspondencetable 213 (the virtual volume correspondence table 212 and external diskcorrespondence table 213 stored on the tape 126), and allocates anactual area to the LU for restoring 112 b in the capacity amountnecessary for restoring. For example, the disk control program 211references the received virtual volume correspondence table 212 andexternal disk correspondence table 213, and references the segmentmanagement table 400 for the number of segments to be copied in therestore operation, and allocates segments for which the In-use (450)value is 0 (unused) to the LU for restoring 112 b. When the size ofsegments which can be allocated to the LU for restoring 112 b and thesize of segments in which data elements stored on the tape 126 (that is,the backed-up data elements) had been stored are not the same, thenumber of segments allocated to the LU for backup at the time of backup,and the number of segments allocated to the LU for restoring 112 b atthe time of restoring, may be different.

In step 8100, the disk control program 211 transmits, to the virtualdisk library apparatus 120, the virtual volume correspondence table 212and external disk correspondence table 213, with restore destinationinformation appended. Specifically, for example, as shown in FIG. 10,the disk control program 211 appends the restore destination segmentnumber 1060 to the physical/logical management table 500, so that dataelements which had been stored in the physical area corresponding tosegment number 1030 are restored to the physical area corresponding tothe segment indicated by the restore destination segment number 1060.The restore destination segment number 1060 is the number of the segmentallocated in step 8090. The disk control program 211 updates to thelatest state both the segment management table 400 and the external diskcorrespondence table 213, and transmits these to the virtual disklibrary apparatus 120.

In step 9010, the restore control program 314 of the virtual disklibrary apparatus 120 receives the virtual volume correspondence table212 and external disk correspondence table 213, with restore destinationinformation appended, which have been transmitted from the storagevirtualization apparatus 110.

In step 9020, the restore control program 314 references the virtualvolume correspondence table 212 and external disk correspondence table213 to which restore destination information has been appended, whilecopying (restoring) backup data elements from the tape 126 on which thebackup data elements (that is, the data elements for restoring) arestored to the physical area on the disk 122 which is to become theactual area of the restore destination. Specifically, when for examplerestoring the LU LUN0 (1011) shown in FIG. 10, the restore controlprogram 314 copies backup data elements stored in the physical areacorresponding to segment number 1 (1021) (at this time, data elementsstored on tape 126) to the physical area corresponding to the segmentwith restore destination segment number 1 (1061). The position of thephysical area of the segment with restore destination segment number 1(1061) can be identified by referencing the segment management table 400and external disk correspondence table 213. Similarly, the restorecontrol program 314 copies backup data elements which had been stored inthe physical area corresponding to the segment of segment number 2(1022) from the tape 126 to the physical area corresponding to thesegment of restore destination segment number 2 (1062), and copies thebackup data elements which had been stored in the physical areacorresponding to the segment of segment number 3 (1023) from the tape126 to the physical area corresponding to the segment of restoredestination segment number 7 (1063). The restore control program 314 cancalculate where on the tape 126 backup data elements stored in physicalareas corresponding to segments of which segment numbers are storedbased on, for example, the order from the top of a segment number in asegment number group corresponding to the backed-up LU in thephysical/logical management table 500, the sizes of segments stored inthe backed-up data, and the ratio of compression (compression ratio)executed by the tape drive 123 at the time of storing of data elementsto tape 126. Or, in place of this method, for example, when the backupcontrol program 313 copies data elements to the tape 126 from thephysical area corresponding to the segments of the backup source, theaddresses on the copy destination tape 126 may be appended to thesegment numbers of the copy source segments in the physical/logicalmanagement table 500, and at the time of the restore operation, therestore control program 314 may reference this physical/logicalmanagement table 500 to identify the stored locations on the tape 126 ofbackup data elements which had been stored in the physical areascorresponding to segments with which segment numbers.

In step 9030, after completion of restoring of the LU for restoring, therestore control program 314 notifies the storage virtualizationapparatus 110 of the completion of restoring of the LU for restoring 112b.

In step 9040, the storage virtualization apparatus 110 receives thenotification of the completion of restoring of the LU for restoring.

In step 9050, in response to the notification of restore completion, thedisk control program 211 of the storage virtualization apparatus 110permits writing to the LU for restoring 112 b from a higher-level device(the host computer 100) (that is, cancels the write-prohibited state).The disk control program 211 can notify the virtual disk libraryapparatus 120 of the cancellation of the write-prohibited state.

In step 9060, in response for example to the notification ofcancellation of the write-prohibited state, the restore control program314 of the virtual disk library apparatus 120 notifies thebackup/restore control instruction program 102 of the host computer 100of the completion of restoring of the LU for restoring 112 b.

The above is an explanation of the processing flow of restoreprocessing. In this processing flow, for example in step 9050 the diskcontrol program 211 of the storage virtualization apparatus 110 may copythe restore destination SN 1060 appended to the physical/logicalmanagement table 500 to the segment number 1030, and may delete thecolumn of restore destination SNs 1060. By this means, thephysical/logical management table 500 can be put into the most recentstate (that is, the state in agreement with completion of restoring ofthe LU for restoring 112 b).

Thus by means of the above-described first embodiment, by transmittingthe virtual volume correspondence table 212 and external diskcorrespondence table 213 between the storage virtualization apparatus110 and the virtual disk library apparatus 120, during volume-unitbackup of virtual volumes 112 a, 112 b which present to a higher-leveldevice virtual capacities different from the actual areas, backup of theactual capacity amount rather than the virtual capacity can beperformed. Further, during a restore operation, restoring of the actualcapacity amount at the time of backup, rather than the virtual capacityof the virtual volume which is the restore destination, can beperformed.

Second Embodiment

Below, a second embodiment of the invention is explained. The followingexplanation primarily addresses points of difference with the firstembodiment, and points in common with the first embodiment are omittedor simplified.

FIG. 11 shows an example of the configuration of a computer system inthe second embodiment of the invention. FIG. 12 shows an example of theconfiguration of the virtual disk array controller 1200 in the secondembodiment of the invention. FIG. 13 shows an example of storage areason a disk 122. The configuration example of the disk array controller111 is the same as in the first embodiment.

The backup/restore control instruction program 102 has a function foroutputting an instruction to the storage virtualization apparatus 110,prior to backup initiation, to prohibit writing to the LU for backup,and a function for outputting an instruction to the storagevirtualization apparatus 110, after the completion of backup, to permitwriting to the LU for backup. The backup/restore control instructionprogram 102 further has a function for outputting an instruction to thestorage virtualization apparatus 110, prior to restore initiation, toprohibit writing to the LU for restoring, and a function for outputtingan instruction to the storage virtualization apparatus 110, after thecompletion of restoring, to permit writing to the LU for restoring.

The storage virtualization apparatus 110 comprises one or more (one, forexample) pools 1110 comprising a plurality of external disks 114. A pool1110 may comprise a single external disk 114. A pool 1110 comprises oneor a plurality of external disks 114, and each segment of each externaldisk 114 corresponds to a physical area of one of the disks 122 amongthe plurality of disks 122. Hence, it can effectively be said that apool 1110 comprises a plurality of disks 122. The disk control program211 has a function for allocating as necessary to a virtual volume 112,as an actual area, a segment from a pool 1110. A pool 1110 is used by aplurality of virtual volumes 112 a, 112 b, and different storage areasof the same external disk 114 may be used by a virtual volume 112 a anda virtual volume 112 b. Similarly to the first embodiment, an externaldisk 114 corresponds to a disk 122, and the correspondence relation ismanaged using an external disk correspondence table 213. As shown inFIG. 13, the information of a virtual volume correspondence table 212and external disk correspondence table 213 corresponding to virtualvolumes 112 a, 112 b to which segments are allocated is stored, asvirtual volume information 1310, on the disk 122 having the physicalareas corresponding to the segments which can be actual areas of thevirtual volumes 112 a, 112 b. For example, virtual volume information1310 is stored in the beginning portion of the storage area of the disk122, and thereafter, segments which can be allocated to the virtualvolumes 112 a, 112 b (physical areas) begin. The disk control program211 has a function to reconstruct the actual areas of the virtualvolumes 112 a, 112 b by referencing the virtual volume information 1310of the disk 122 comprised by the pool 1110 (a function for updating thevirtual volume correspondence table 212 and external disk correspondencetable 213 such that the contents are the same as the virtual volumeinformation 1310).

The size of a prescribed area in which the virtual volume information1310 is stored is set based on the number of physical areas of the disk122 storing the virtual volume information 1310, and similar. By thismeans, the virtual volume information 1310 can be prevented fromexceeding the prescribed area, even when the size of the virtual volumeinformation 1310 increases as a result of the appending of data to thevirtual volume information 1310. Updating of the virtual volumeinformation 1310 is executed by for example the disk control program 211of the storage virtualization apparatus 110 each time a physical area(segment) of the disk 122 storing the virtual volume information 1310 isallocated to a virtual volume 112 a or 112 b, or allocation of aphysical area (segment) is canceled.

The virtual disk array controller 1200 comprises a differentialmanagement program 1210 and a differential management table 1400. Inaddition, a differential bitmap 1500 (see FIG. 15) is stored on the disk122.

The differential management program 1210 has a function for using thedifferential management bitmap 1500 to perform differential managementof the disk 122. For example, the differential bitmap 1500 can be usedto perform management by setting the bits for storage areas to whichwriting has been performed to 1 and bits for storage areas to whichwriting has not been performed to 0.

The differential management table 1400 and differential bitmap 1500 areused to perform differential management of disks 122. As shown in FIG.14, the disk ID 1410, differential bitmap number 1420, differentialmanagement size 1430, and differential bitmap storage position 1440 arestored in the differential management table 1400. The disk ID 1410 is aunique identification number for the disk 122 for which differentialmanagement is performed. The differential bitmap number 1420 is a uniqueidentification number for the differential bitmap 1500 corresponding tothe disk 122 with the disk ID 1410. The differential management size1430 indicates the size corresponding to one bit of the differentialbitmap. The differential bitmap storage position 1440 indicates where onthe disk 122 the differential bitmap is stored. For example, if thedifferential bitmap storage position 1440 is 100:0-1000 (1441), thenstorage is 1000 from LBA 0 of disk ID 100. The differential bitmapstorage position may indicate that storage is in cache memory 330 ratherthan on the disk 122, in order to enable faster referencing of thebitmap. One differential bitmap 1500 may for example be prepared for onedisk 122. If for example the differential management size 1430 is 1 MB,then in the differential bitmap 1500, 1510 a and 1510 b are thedifferential bits corresponding to the blocks from the beginning of thestorage area of the disk 122 to 1 MB, and from 1 MB to 2 MB,respectively. When one of the corresponding blocks has been updated(written), the differential bit is inverted. For example, 1510 a, 1510b, and 1510 e indicate the blocks have not been updated (have not beenwritten), whereas 1510 c and 1510 d indicate that there has beenupdating (writing).

The virtual disk library apparatus 120 can determine the segments usedas actual areas of a virtual volume 112 on a disk 122 comprised by apool 1110 by referencing the differential management table 1400 and thedifferential bitmap 1500. For example, on a disk 122 comprised by a pool1110, in a state in which none of the segments (storage areas) areallocated as actual areas of virtual volumes 112 a, 112 b, thedifferential bitmap 1500 of the disk 122 comprised by the pool 1110 canbe reset (for example, cleared to all 0's). Thereafter, when there isallocation as an actual area of a virtual volume 112, writing alwaysoccurs to the physical area allocated as an actual area, and so aphysical area for which the bit in the differential bitmap 1500 isinverted (to a 1 bit) can be recognized as a physical area being used asan actual area of a virtual volume 112 a, 112 b. Bits comprised by adifferential bitmap 1500 may each be associated not with a physicalarea, but with each of a plurality of blocks comprised by a physicalarea.

FIG. 16 shows the flow of processing in backup processing of the secondembodiment of the invention.

In step 16010, the backup/restore control instruction program 102 of thehost computer 100 transmits an instruction to the storage virtualizationapparatus 110 prohibiting writing to the LU for backup, and the storagevirtualization apparatus 110 receives the write-prohibit instruction.Here, the LU for backup is the LU to which are allocated segments withinthe pool for backup, described below. For example, when pool 1110 is apool for backup, the virtual volumes 112 a and 112 b are LUs for backup.

In step 16020, in response to the write-prohibit instruction, the diskcontrol program 211 of the storage virtualization apparatus 110prohibits writing to the LUs for backup 112 a, 112 b.

In step 16030, the backup/restore control instruction program 102 of thehost computer 100 transmits to the virtual disk library apparatus 120 abackup initiation instruction, specifying a pool for backup, and thevirtual disk library apparatus 120 receives this backup initiationinstruction. For example, in the backup initiation instruction, the LUNsof all the disks 122 comprised by the pool 1110 for backup, and the tape126 to serve as the backup destination, may be specified. The LUNs ofthe disks 112 comprised by the pool 1110 can for example be managed in atable or similar, not shown, in the host computer 100. The LUNs of thedisks 122 comprised by the pool 1110 for backup may for example be inputmanually by a user of the host computer 100, or an identifier of thepool 1110 for backup may be input by the user, so that backup/restorecontrol instruction program 102 identifies the LUNs of disks 122corresponding to the identifier.

In step 16040, in response to the backup initiation instruction, thebackup control program 313 of the virtual disk library apparatus 120copies, to the tape 126 serving as the backup destination, each of thedifferential bitmaps 1500 for each of the disks 122 comprised by thepool for backup and the differential management table 1400. The copydestination of the differential bitmaps 1500 and the differentialmanagement table 1400 may be the beginning portion of the tape 126serving as the backup destination, or another prescribed position, ormay be an arbitrary position. A table, not shown, may be used to manage,within the virtual disk library apparatus 120, the locations of storageon the tape 126 of the differential bitmaps 1500 and the differentialmanagement table 1400.

In step 16050, the backup control program 313 references each of thedifferential bitmaps 1500 while copying data elements in physical areascorresponding to actual areas in the pool for backup (segments allocatedto virtual volumes 112 a, 112 b) from disks 122 to the tape 126 which isthe backup destination. For example, the backup control program 313references the differential bitmaps 1500, and copies data elementsstored in blocks corresponding to inverted bits to the tape 126 which isthe backup destination.

In step 16060, after completion of backup of the pool for backup, thebackup control program 313 notifies the backup/restore controlinstruction program 102 of the host computer 100 of the completion ofbackup of the pool for backup.

In step 16070, in response to the notification of backup completion, thebackup/restore control instruction program 102 of the host computer 100transmits to the storage virtualization apparatus 110 an instruction topermit writing to backed-up LUs, and the storage virtualizationapparatus 110 receives this write-permit instruction.

In step 16080, in response to the write-permit instruction, the diskcontrol program 211 of the storage virtualization apparatus 110 permitswriting to the backed-up LUs.

FIG. 17 shows the processing flow of restore processing in the secondembodiment of the invention.

In step 17010, the backup/restore control instruction program 102 of thehost computer 100 transmits, to the storage virtualization apparatus110, an instruction prohibiting writing by a higher-level device to theLUs to be restored, and the instruction is received by the storagevirtualization apparatus 110. In this processing flow, similarly to thefirst embodiment, the restore destination LUs and the LUs for restoring(that is, the LUs which are the backup source) are assumed to be thesame. Restoring is performed in pool units, similarly to backup, and sothe LUs for restoring are virtual volumes 112 a, 112 b.

In step 17020, the disk control program 211 of the storagevirtualization apparatus 110 prohibits writing by higher-level devicesto the LUs for restoring 112 a, 112 b.

In step 17030, the backup/restore control instruction program 102 of thehost computer 100 transmits, to the virtual disk library apparatus 120,a restore initiation instruction specifying the pool for restoring, andthe virtual disk library apparatus 120 receives this restore initiationinstruction. For example, in the restore initiation instruction, thetape 126 to serve as the restore source, and the LUNs of all disks 122comprised by the pool for restoring 1110, are specified.

In step 17040, the restore control program 314 of the virtual disklibrary apparatus 120 formats all the disks 122 comprised by the poolfor restoring 1110 (that is, all the disks 122 serving as the restoredestination). In this formatting, for example, all areas (all segments)of each disk 122 comprised by the pool 1110 are overwritten with 0's.

In step 17050, the restore control program 314 of the virtual disklibrary apparatus 120 restores each of the differential bitmaps 1500corresponding to each of the disks 122 comprised by the pool forrestoring 1110 to the state at the time of backup, using thedifferential bitmaps 1500 stored on the tape 126 which is the restoresource (that is, causes each of the differential bitmaps 1500corresponding to each disk 122 comprised by the pool for restoring 1110to have the same content as the differential bitmaps 1500 stored on thetape 126 which is the restore source).

In step 17060, the restore control program 314 references the restoreddifferential bitmaps 1500 while copying (restoring) backup data from thetape 126 which is the restore source to the physical areas of disks 122which are the actual areas of the restore destination. The locations towhich backup data is copied are controlled by for example executingbackups according to prescribed rules and executing the restoreoperation based on the prescribed rules. Specifically, for example, atthe time of backup, copying is executed in order from the segments withthe smallest segment numbers, on the disks 122 with the smallest LUNs,among the disks 122 comprised by the pool for backup. At the time ofrestore also, restoring is performed in order from the backup datastored to segments with the smallest segments numbers on the disks 122with the smallest LUNs. The starting and ending locations of backup datastoring one segment on the tape 126 can be identified based on theactual ratio of compression (compression ratio) of the tape drive 123.

In step 17070, after completion of restoring of the pool for restoring,the restore control program 314 notifies the backup/restore controlinstruction program 102 of the host computer 100 of the completion ofrestoring of the pool for restoring.

In step 17080, in response to the notification of restore completion,the backup/restore control instruction program 102 of the host computer100 transmits, to the storage virtualization apparatus 110, aninstruction to permit writing by a higher-level device to the restoredLUs 112 a, 112 b, and the storage virtualization apparatus 110 receivesthe write-permit instruction.

In step 17090, in response to the write-permit instruction, the diskcontrol program 211 of the storage virtualization apparatus 110references the virtual volume information 1310 of each disk 122 in therestored LUs 112 a, 112 b, and reconstructs allocation of actual areas(segments) to the virtual volumes 112 a, 112 b. Specifically, the diskcontrol program 211 updates the virtual volume correspondence table 212and external disk correspondence table 213 such that the contents arethe same as the virtual volume information 1310 for each disk 122.

In step 17100, the disk control program 211 permits writing by ahigher-level device to the restored LUs 112 a, 112 b.

Thus according to the above-described second embodiment, throughdifferential management of the disks 122 comprised by the pool 1110 inthe virtual disk library apparatus 120, backup of the actual capacityamount is possible. In the case of a restore operation, restoring of theactual capacity amount for which backup has been performed is possible.Each of the differential bitmaps 1500 may be stored in control memory310, instead of or in addition to being stored on disks 122. Conversely,the differential management table 1400 may be stored on disks 122instead of or in addition to being stored in control memory 310.

The following is a summary of the points of difference between the firstembodiment and the second embodiment.

In the first embodiment, backup processing and restore processing caneach be performed in virtual volume units. Specifically, for example,when the object of backup and of restore is a virtual volume 112 b, inbackup processing data stored in actual areas (segments) allocated tothe virtual volume 112 b is copied to a tape 126 by transmitting thevirtual volume correspondence table 212 and external disk correspondencetable 213 from the storage virtualization apparatus 110 to the virtualdisk library apparatus 120. In restore processing, the data of theactual capacity amount of the virtual volume 112 b is copied from thetape 126 to disks 122. However, upon completion of the restoreoperation, the numbers of segments allocated to the virtual volume 112 band the numbers of segments allocated to the virtual volume 112 b at thetime of backup initiation may not be the same.

On the other hand, in the second embodiment, backup processing andrestore processing are each performed in pool units, rather than invirtual volume units. That is, even if for example there was a desire toback up only virtual volume 112 b, it would not be possible to back upvirtual volume 112 b alone; instead, the data stored in allocatedsegments in the pool 1110 would be backed up. Allocated segments includenot only segments allocated to the virtual volume 112 b, but alsosegments allocated to the virtual volume 112 a, and so as a result notonly virtual volume 112 b, but also virtual volume 112 a, which receivessegments allocated from the same pool 1110, would be backed up. However,in the second embodiment, which segments have been allocated in whichdisk 122 is managed by the virtual disk library apparatus 120, and sothere is no need to transmit virtual volume correspondence tables 212 orexternal disk correspondence tables 213 from the storage virtualizationapparatus 110 to the virtual disk library apparatus 120.

Third Embodiment

Below, a third embodiment of the invention is explained. The followingexplanation primarily addresses points of difference with the firstembodiment, and points in common with the first embodiment are omittedor simplified.

FIG. 18 shows an example of the configuration of a computer system inthe third embodiment of the invention. FIG. 19 shows an example of theconfiguration of the virtual disk array controller 1810 in the thirdembodiment.

The host computer 100 and virtual disk library apparatus 120 areconnected using fiber channel 140, and exchange data, processingrequests, and similar. The host computer 100 and virtual disk libraryapparatus 120 may be connected by a LAN (Local Area Network) or othercommunication network, or may be connected by dedicated circuits orsimilar.

The virtual disk library apparatus 120 comprises the virtual disk arraycontroller 1810, a plurality of virtual volumes 1820, disks, 122, and atape library apparatus 123.

The virtual disk array controller 1810 comprises a FE/IF portion 300,which is the interface with the host computer 100; local memory(hereafter control memory) 310, which stores a disk control program1910, tape library control program 312, backup control program 313,restore control program 314, and virtual volume correspondence table1920; a processor (for example, a CPU; hereafter called a controlprocessor) 320, which executes the disk control program 1910, tapelibrary control program 312, backup control program 313, restore controlprogram 314, and virtual volume correspondence table 1920; cache memory330, which temporarily stores information; a disk IF portion 340, whichinterfaces with disks 122; and, a data IF portion 350, which interfaceswith the tape library apparatus 123.

The disk control program 1910 has a function for using a virtual volumecorrespondence table 1920 to handle a virtual volume 1820 which presentsa virtual capacity to the host (for example, an application 101). Theactual areas of the virtual volume 1820 are segments on a disk 122; afunction is provided to present to the host a virtual capacity equal toor greater than the actual capacity as the storage capacity of thevirtual volume 1820. A function is also provided for managing andcontrolling disks 122 of the virtual disk library apparatus 120.

The segment management table 2000 of FIG. 20 and the physical/logicalmanagement table 2100 of FIG. 21 together constitute a virtual volumecorrespondence table 1920.

The segment management table 2000 is the same as the segment managementtable 400 of FIG. 4, other than the fact that the external disk ID 410in the segment management table 400 has been changed to a disk ID 2010.The disk ID 2010 is a unique identification number for a disk 122,determined by the disk control program 1910.

The physical/logical management table 2100 is the same as thephysical/logical management table 500 of FIG. 5.

FIG. 22 shows the processing flow in backup processing of the thirdembodiment of the invention.

In step 22010, the backup/restore control instruction program 102 of thehost computer 100 transmits a backup initiation instruction for the LUfor backup 112 b to the virtual disk library apparatus 120, and thevirtual disk library apparatus 120 receives this backup initiationinstruction.

In step 22020, in response to the backup initiation instruction, thebackup control program 313 of the virtual disk library apparatus 120prohibits writing to the LU for backup 112 b by a higher-level device.

In step 22030, the backup control program 313 copies the virtual volumecorrespondence table 1920 necessary at the time of restore of the LU forbackup 112 b to the tape 126 which is the backup destination.

In step 22040, the backup control program 313 references the virtualvolume correspondence table 1920 while copying data elements stored inactual areas of the LU for backup 112 b from the disk 122 to the tape126 which is the backup destination.

In step 22050, after completion of backup of the LU for backup, thebackup control program 313 permits writing to the backed-up LU 112 b.

In step 22060, the backup control program 313 notifies thebackup/restore control instruction program 102 of the host computer 100of the completion of backup of the backed-up LU 112 b.

FIG. 23 shows the processing flow of restore processing in the thirdembodiment of the invention.

In step 23010, the backup/restore control instruction program 102 of thehost computer 100 transmits a restore initiation instruction for the LUfor restoring 112 b to the virtual disk library apparatus 120, and thevirtual disk library apparatus 120 receives this restore initiationinstruction.

In step 23020, in response to the restore initiation instruction, therestore control program 314 of the virtual disk library apparatus 120prohibits writing by a higher-level device to the LU for restoring 112b.

In step 23030, the restore control program 314 resets the allocation ofactual areas of the LU for restoring 112 b.

In step 23040, the restore control program 314 reads the virtual volumecorrespondence table 1920 from the tape 126 which is the restore source.

In step 23050, the restore control program 314 references the virtualvolume correspondence table 1920 stored on the tape 126, and allocatesactual areas, in the actual capacity amount necessary for the restoreoperation, to the LU for restoring 112 b.

In step 23060, the restore control program 314 creates a virtual volumecorrespondence table with the restore destination information appended,as shown in FIG. 10.

In step 23070, the restore control program 314 references the virtualvolume correspondence table with restore destination informationappended, while copying (restoring) data elements from the tape 126 onwhich is stored the backup data to actual areas of the restoredestination.

In step 23080, after completion of restoring of the LU for restoring,the restore control program 314 permits writing by a higher-level deviceto the restored LU 112 b.

In step 23090, the restore control program 314 notifies thebackup/restore control instruction program 102 of the host computer 100of the completion of restoring of the restored LU.

According to the above-described third embodiment, in a systemcomprising a host computer 100 and a virtual disk library apparatus 120,a virtual volume correspondence table 1920 can be used to back up theactual capacity amount. In the event of a restore operation, restoringnot of the virtual capacity of the restore destination virtual volume,but of the backed-up actual capacity amount is possible.

Fourth Embodiment

Below, a fourth embodiment of the invention is explained. The followingexplanation primarily addresses points of difference with the thirdembodiment, and points in common with the third embodiment are omittedor simplified.

The example of the configuration of a computer system of the fourthembodiment is the same as in the third embodiment. The flow of backupprocessing is also the same as in the third embodiment, but a portion ofthe flow of restore processing is different from that of the thirdembodiment.

FIG. 24 shows the processing flow of restore processing in the fourthembodiment of the invention.

In step 24010, the backup/restore control instruction program 102 of thehost computer 100 transmits a restore initiation instruction for the LUfor restoring 112 b to the virtual disk library apparatus 120, and thevirtual disk library apparatus 120 receives this restore initiationinstruction.

In step 24020, in response to the restore initiation instruction, therestore control program 314 prohibits writing by a higher-level deviceto the LU for restoring 112 b.

In step 24030, the restore control program 314 resets the allocation ofactual areas of the LU for restoring 112 b.

In step 24040, the restore control program 314 reads the virtual volumecorrespondence table 1920 from the tape 126 which is the restore source.

In step 24050, the restore control program 314 references the virtualvolume correspondence table 1920 which had been stored on the tape 126which is the restore source, while copying (restoring) data elementsfrom the tape 126 on which the backup data is stored to the logicaladdress positions of the restore destination virtual volume 1820. Thelogical address positions of the virtual volume 1820 are, for example,address positions indicated by LUN LBA (START) 540 and LUN LBA (END)550, shown in FIG. 21. By writing to the virtual volume 1820, data copyprocessing (restore processing) is performed while allocating actualareas to the virtual volume 1820, for example by means of technologydisclosed in Japanese Patent Laid-open No. 2003-15915.

In step 24060, after completion of restoring of the LU for restoring,the restore control program 314 permits writing by a higher-level deviceto the restored LU.

In step 24070, the restore control program 314 notifies thebackup/restore control instruction program 102 of the host computer 100of the completion of restoring of the restored LU.

Thus according to the above-described fourth embodiment, in a systemcomprising a host computer 100 and a virtual disk library apparatus 120,a virtual volume correspondence table 1920 can be used to perform abackup of the actual capacity amount. In the event of a restoreoperation, restoring of the backed-up actual capacity amount ispossible.

The points of difference between the third embodiment and the fourthembodiment may for example be summarized as follows. In the thirdembodiment, the restore destination is not the virtual volume 112 b, butis the segments of disks 122 which are the actual areas of the virtualvolume 112 b. On the other hand, in the fourth embodiment, the restoredestination is the virtual volume 112 b itself, and each time restoring(copying) to the virtual volume 112 b is performed, the backed-up dataelements (data elements to be restored) are written to the segmentsallocated to addresses corresponding to the restore destination.

In the above, a number of preferred embodiments of the invention havebeen explained; however, these embodiments are merely examples used inexplaining the invention, and the scope of the invention is not limitedto these embodiments. This invention can be implemented in a variety ofother forms as well.

1. A storage control device provided for a virtualization system whichallocates unallocated segments, among a plurality of segments, accordingto a write operation to a virtual volume which is a virtual logicalvolume provided to a higher-level device, and writes data elements tothe allocated segments according to the write operation, comprising: oneor more first storage devices, related to said plurality of segments; asecond storage device; and a backup control portion which uses writemanagement information, which is information used to manage locations ofwrite operations in said one or more first storage devices, to specifyone or more locations in which writing has occurred in said one or morefirst storage devices, and backs up one or more data elements stored insaid specified one or more locations to said second storage device. 2.The storage control device according to claim 1, further comprising: astorage portion which stores said write management information at thetime of backup; and a restore control portion which reads said writemanagement information at said time of backup, and restores said one ormore data elements stored in said second storage device to said one ormore locations specified from said read-out write managementinformation, or to one or more new locations specified from new writemanagement information representing one or more new locationscorresponding to said one or more locations, wherein said new writemanagement information is information generated on the basis of saidread-out write management information.
 3. The storage control deviceaccording to claim 1, wherein said storage control device is connectedto a virtualization apparatus provided for said virtualization system,said virtualization apparatus comprises: a storage resource which storesallocation management information, which is information indicating whichsegment, among a plurality of segments forming one or more virtual firststorage devices based on said one or more first storage devices, isallocated to said virtual volume, and correspondence managementinformation, which indicates to which physical area of said one or morefirst storage devices each of said plurality of segments corresponds; awrite control portion which receives a first write request for data forwriting to said virtual volume from said higher-level device, inresponse to the first write request selects one or more unallocatedsegments from said plurality of segments based on said allocationmanagement information, allocates the selected one or more unallocatedsegments to said virtual volume, updates said allocation managementinformation to information indicating allocation of the one or moresegments to said virtual volume, specifies the one or more physicalareas corresponding to the allocated one or more segments in use of saidcorrespondence management information, and transmits to said storagecontrol device a second write request to write said data for writing tothe specified one or more physical areas; and a write managementinformation transmission portion which transmits, to said storagecontrol device, said write management information comprising saidallocation management information and said correspondence managementinformation, and wherein said storage control device further has a writeexecution portion which writes said data for writing according to thesecond write request from said virtualization apparatus to said one ormore physical areas, in said one or more first storage devices,according to the second write request; and said one or more locationsspecified by said backup control portion are one or more physical areasin said one or more first storage devices, specified in use of saidwrite management information from said virtualization apparatus.
 4. Thestorage control device according to claim 3, further comprising: astorage portion which stores said write management information at thetime of backup; and a restore control portion which reads said writemanagement information at the time of said backup, transmits theread-out write management information to said virtualization apparatus,receives from said virtualization apparatus new write managementinformation representing one or more new physical areas corresponding toone or more new said physical areas generated by said virtualizationapparatus based on the write management information, and restores saidone or more data elements stored in said second storage device to saidone or more new physical areas specified from said new write managementinformation.
 5. The storage control device according to claim 1, whereinsaid storage control device is connected to a virtualization apparatusprovided for said virtualization system, said virtualization apparatuscomprises: a storage resource which stores allocation managementinformation, which is information indicating which segment, among aplurality of segments forming one or more virtual first storage devicesbased on said one or more first storage devices, is allocated to saidvirtual volume, and correspondence management information, whichindicates to which physical area of said one or more first storagedevices each of said plurality of segments corresponds; and a writecontrol portion which receives a first write request for data forwriting to said virtual volume from said higher-level device, inresponse to the first write request selects one or more unallocatedsegments from said plurality of segments based on said allocationmanagement information, allocates the selected one or more unallocatedsegments to said virtual volume, updates said allocation managementinformation to information indicating allocation of the one or moresegments to said virtual volume, specifies the one or more physicalareas corresponding to the allocated one or more segments in use of saidcorrespondence management information, and transmits to said storagecontrol device a second write request to write said data for writing tothe specified one or more physical areas, and wherein said storagecontrol device further has a write execution portion which writes saiddata for writing according to said second write request from saidvirtualization apparatus to said one or more physical areas, in said oneor more first storage devices, according to the second write request,and updates said write management information to information indicatingoccurrence of writing to said one or more physical areas, according tothe writing; and, said one or more locations specified by said backupcontrol portion are one or more physical areas in said one or more firststorage devices, specified in use of said write management informationafter updating.
 6. The storage control device according to claim 5,further comprising: a storage portion which stores said write managementinformation at the time of backup; and a restore control portion whichreads said write management information at the time of said backup, andrestores respectively said one or more data elements stored in saidsecond storage device to one or more physical areas specified from theread-out write management information.
 7. The storage control deviceaccording to claim 1, further comprising: a storage resource whichstores said write management information indicating which segment amonga plurality of segments has been allocated to said virtual volume; and awrite control portion which provides said virtual volume to saidhigher-level device, receives a write request for data for writing fromsaid higher-level device, selects one or more unallocated segments fromamong said plurality of segments in response to the write request basedon said write management information, allocates the selected one or moreunallocated segments to said virtual volume, writes said data forwriting to the allocated one or more segments, and updates said writemanagement information to information indicating allocation of the oneor more segments to said virtual volume, wherein each of said pluralityof segments is a storage area forming said one or more first storagedevices; and said write management information is information indicatingwhich segment among said plurality of segments has been allocated tosaid virtual volume.
 8. The storage control device according to claim 7,further comprising: a storage portion which stores said write managementinformation at the time of backup; and a restore control portion whichreads said write management information at the time of said backup,associates one or more new segments with each of said one or moresegments specified from the write management information, and restores,to the one or more new segments, said one or more data elements storedin said second storage device.
 9. The storage control device accordingto claim 7, further comprising a restore control portion which updatessaid write management information stored in said storage resource toinformation indicating that none of said plurality of segments isallocated to said virtual volume, reads said one or more data elementsfrom said second storage device, selects segments for writing of theread-out data elements from said plurality of segments to allocate thesegments to said virtual volume, restores said read-out data elements tothe allocated segments, and updates said write management information toinformation indicating allocation of the segments to said virtualvolume.
 10. The storage control device according to claim 1, whereineach of said one or more first storage devices is a random access-typestorage device, and said second storage device is a sequentialaccess-type storage device.
 11. A virtualization system, comprising: avirtualization apparatus; and a storage control device connected to saidvirtualization apparatus, wherein said virtualization apparatuscomprises: a storage resource which stores allocation managementinformation, which is information indicating which segment among aplurality of segments forming one or more virtual first storage devicesbased on one or more first storage devices is allocated to virtualvolume, and correspondence management information, which indicates towhich physical area of said one or more first storage devices each ofsaid plurality of segments corresponds; a write control portion whichreceives a first write request for data for writing to said virtualvolume from said higher-level device, in response to the first writerequest selects one or more unallocated segments from said plurality ofsegments based on said allocation management information, allocates theselected one or more unallocated segments to said virtual volume,updates said allocation management information to information indicatingallocation of the one or more segments to said virtual volume, specifiesthe one or more physical areas corresponding to the allocated one ormore segments respectively in use of said correspondence managementinformation, and transmits to said storage control device a second writerequest to write said data for writing to the specified one or morephysical areas; and a write management information transmission portionwhich transmits to said storage control device said write managementinformation comprising said allocation management information and saidcorrespondence management information, and wherein said storage controldevice comprises: said one or more first storage devices; a secondstorage device; and a backup control portion which specifies one or morephysical areas in said one or more first storage devices in use of saidwrite management information from said virtualization apparatus, andbacks up one or more data elements stored in said specified one or morephysical areas to said second storage device.
 12. The virtualizationsystem according to claim 11, wherein said virtualization apparatusfurther comprises a segment reallocation portion; said storage controldevice further comprises a storage portion and restore control portion;said storage portion stores said write management information at thetime of backup; said restore control portion reads said write managementinformation at said time of backup, and transmits the read-out writemanagement information to said virtualization apparatus; said segmentreallocation portion associates one or more new segments respectivelywith one or more segments specified in use of said write managementinformation from said storage control device, generates new writemanagement information indicating the one or more new physical areascorresponding to the one or more new segments respectively based on saidwrite management information, and transmits the generated new writemanagement information to said storage control device; and said restorecontrol portion of said storage control device restores respectivelysaid one or more data elements stored in said second storage device tosaid one or more new physical areas specified in use of said new writemanagement information from said virtualization apparatus.
 13. Avirtualization system, comprising: a virtualization apparatus; and astorage control device connected to said virtualization apparatus,wherein said virtualization apparatus comprises: a storage resourcewhich stores allocation management information, which is informationindicating which segment among a plurality of segments forming one ormore virtual first storage devices is allocated to a virtual volumebased on said one or more first storage devices, and correspondencemanagement information, which indicates correspondence between each ofsaid plurality of segments and physical areas in said one or more firststorage devices; and a write control portion which receives a firstwrite request for data for writing to said virtual volume from ahigher-level device, selects one or more unallocated segments from amongsaid plurality of segments in response to the first write request basedon said allocation management information, allocates the one or moreselected unallocated segments to said virtual volume, updates saidallocation management information to information indicating allocationof the one or more segments to said virtual volume, specifies the one ormore physical areas corresponding to the one or more allocated segmentsin use of said correspondence management information, and transmits, tosaid storage control device, a second write request to write said datafor writing to the specified one or more physical areas, and whereinsaid storage control device comprises: said one or more first storagedevices; a second storage device; a write execution portion which writessaid data for writing according to said second write request from saidvirtualization apparatus to said one or more physical areas, in said oneor more first storage devices, according to the second write request,and updates said write management information to information indicatingoccurrence of writing to said one or more physical areas according tothe writing; and a backup control portion which uses said writemanagement information after updating to specify one or more physicalareas in which writing has occurred in said one or more first storagedevices, and backs up one or more data elements stored in the one ormore specified physical areas to said second storage device.
 14. Thevirtualization system according to claim 13, wherein said virtualizationapparatus further comprises an allocation management information storageportion which stores said allocation management information at the timeof backup; said storage control device further comprises a storageportion and a restore control portion; said storage portion stores saidwrite management information at the time of backup; said restore controlportion reads said write management information at said time of backup,and restores, to one or more physical areas specified from the read-outwrite management information, said one or more data elements stored insaid second storage device; and said allocation management informationstorage portion restores, to said storage resource, said allocationmanagement information at the time of backup of said restored one ormore data elements.
 15. A storage control method for allocatingunallocated segments among a plurality of segments according to writingto a virtual volume which is a virtual logical volume provided to ahigher-level device and for writing data elements according to thewriting to the allocated segments, wherein write management information,which is information used to manage locations in which writing hasoccurred in one or more first storage devices related to said pluralityof segments, is used to specify one or more locations where writing hasoccurred in said one or more storage devices; and one or more dataelements stored in said specified one or more locations are backed up toa second storage device.
 16. The storage control method according toclaim 15, wherein said write management information is stored at thetime of backup; said write management information at said time of backupis read, and said one or more data elements stored in said secondstorage device are restored to said one or more locations specified fromsaid read-out write management information, or to one or more newlocations specified from new write management information indicatingsaid one or more new locations corresponding to said one or morelocations; and said new write management information is informationgenerated based on said read-out write management information.
 17. Avirtualization apparatus connected to a storage control device havingone or more first storage devices, comprising: a storage resource whichstores allocation management information, which is informationindicating which segment among a plurality of segments forming one ormore virtual first storage devices is allocated to a virtual volumebased on said one or more first storage devices, and correspondencemanagement information, which indicates correspondence between each ofsaid plurality of segments and physical areas in said one or more firststorage devices; a write control portion which receives a first writerequest for data for writing to said virtual volume from a higher-leveldevice, selects one or more unallocated segments from among saidplurality of segments in response to the first write request based onsaid allocation management information, allocates the one or moreselected unallocated segments to said virtual volume, updates saidallocation management information to information indicating allocationof the one or more segments to said virtual volume, specifies the one ormore physical areas corresponding to the one or more allocated segmentsrespectively in use of said correspondence management information, andtransmits, to said storage control device, a second write request towrite said data for writing to the specified one or more physical areas;and a write management information transmission portion which transmits,to said storage control device, said write management informationcomprising said allocation management information and saidcorrespondence management information.
 18. The virtualization apparatusaccording to claim 17, further comprising a segment reallocation portionwhich associates one or more new segments respectively with one or moresegments specified in use of said write management information from saidstorage control device, generates new write management informationindicating the one or more new physical areas corresponding to the oneor more new segments based on said write management information, andtransmits the generated new write management information to said storagecontrol device.
 19. A virtualization apparatus connected to a storagecontrol device having one or more first storage devices, comprising: astorage resource which stores allocation management information, whichis information indicating which segment among a plurality of segmentsforming one or more virtual first storage devices is allocated to avirtual volume based on said one or more first storage devices, andcorrespondence management information, which indicates correspondencebetween each of said plurality of segments and physical areas in saidone or more first storage devices; a write control portion whichreceives a first write request for data for writing to said virtualvolume from a higher-level device, selects one or more unallocatedsegments from among said plurality of segments in response to the firstwrite request based on said allocation management information, allocatesthe one or more selected unallocated segments to said virtual volume,updates said allocation management information to information indicatingallocation of the one or more segments to said virtual volume, specifiesthe one or more physical areas corresponding to the one or moreallocated segments in use of said correspondence management information,and transmits, to said storage control device, a second write request towrite said data for writing to the specified one or more physical areas;and an allocation management information storage portion which storessaid allocation management information at the time of backup.
 20. Astorage control device provided for a virtualization system whichallocates unallocated segments, among a plurality of segments, accordingto a write operation to a virtual volume which is a virtual logicalvolume provided to a higher-level device, and writes data elements tothe allocated segments according to the write operation, comprising: oneor more first storage devices, related to said plurality of segments; asecond storage device; a storage portion which stores write managementinformation at the time of backup, which is write management informationto manage locations where writing has occurred in said one or more firststorage devices; and, a restore control portion which reads said writemanagement information at the time of backup, and restores one or moredata elements stored in said one or more locations among the pluralityof data elements stored in said second storage device, to one or morelocations specified from said read-out write management information, orto one or more new locations specified from new write managementinformation indicating one or more new locations corresponding to saidone or more locations.
 21. The storage control device according to claim20, wherein said storage control device is connected to a virtualizationapparatus provided for said virtualization system; said virtualizationapparatus comprises: a storage resource which stores allocationmanagement information, which is information indicating which segment,among a plurality of segments forming one or more virtual first storagedevices, is allocated to a virtual volume based on said one or morefirst storage devices, and correspondence management information, whichindicates correspondence between each of said plurality of segments andphysical areas in said one or more first storage devices; a writecontrol portion which receives a first write request for data forwriting to said virtual volume from said higher-level device, selectsone or more unallocated segments from among said plurality of segmentsin response to the first write request based on said allocationmanagement information, allocates the one or more selected unallocatedsegments to said virtual volume, updates said allocation managementinformation to information indicating allocation of the one or moresegments to said virtual volume, specifies the one or more physicalareas corresponding to the one or more allocated segments respectivelyin use of said correspondence management information, and transmits, tosaid storage control device, a second write request to write said datafor writing to the specified one or more physical areas; and a writemanagement information transmission portion which transmits, to saidstorage control device, said write management information comprisingsaid allocation management information and said correspondencemanagement information; said storage control device further has a writeexecution portion which writes said data for writing, according to thesecond write request from said virtualization apparatus, to said one ormore physical areas according to the second write request; said storageportion stores said write management information from saidvirtualization apparatus; and said restore control portion transmitssaid read-out write management information to said virtualizationapparatus, receives from said virtualization apparatus new writemanagement information which is generated by said virtualizationapparatus based on the write management information and which indicatesone or more new physical areas corresponding to said one or morephysical areas respectively, and restores said one or more data elementsstored in said second storage device to said one or more new physicalareas specified from said new write management information.
 22. Thestorage control device according to claim 20, wherein said storagecontrol device is connected to a virtualization apparatus provided forsaid virtualization system; said virtualization apparatus comprises: astorage resource which stores allocation management information, whichis information indicating which segment, among a plurality of segmentsforming one or more virtual first storage devices, is allocated to avirtual volume based on said one or more first storage devices, andcorrespondence management information, which indicates thecorrespondence between each of said plurality of segments and physicalareas in said one or more first storage devices; and a write controlportion which receives a first write request for data for writing tosaid virtual volume from said higher-level device, selects one or moreunallocated segments from among said plurality of segments in responseto the first write request based on said allocation managementinformation, allocates the one or more selected unallocated segments tosaid virtual volume, updates said allocation management information toinformation indicating allocation of the one or more segments to saidvirtual volume, specifies the one or more physical areas correspondingto the one or more allocated segments respectively in use of saidcorrespondence management information, and transmits, to said storagecontrol device, a second write request to write said data for writing tothe specified one or more physical areas, said storage control devicefurther has a write execution portion which writes said data for writingaccording to the second write request from said virtualizationapparatus, to said one or more physical areas, in said one or more firststorage devices, according to the second write request, and updates saidwrite management information to information indicating occurrence ofwriting to said one or more physical areas, according to the writeoperation; and said restore control portion restores respectively saidone or more data elements stored in said second storage device to one ormore physical areas specified from said read-out write managementinformation.
 23. The storage control device according to claim 20,further comprising: a storage resource which stores said writemanagement information indicating which segment, among a plurality ofsegments, is allocated to said virtual volume; and a write controlportion which provides said virtual volume to said higher-level device,receives a write request for data for writing from said higher-leveldevice, selects one or more unallocated segments from among saidplurality of segments in response to the write request based on saidwrite management information, allocates the one or more selectedunallocated segments to said virtual volume, writes said data forwriting to the one or more allocated segments, and updates said writemanagement information to information indicating allocation of the oneor more segments to said virtual volume, wherein each of said pluralityof segments is a storage area forming said one or more first storagedevices; said write management information is information indicatingwhich segment, among said plurality of segments, is allocated to saidvirtual volume; and said restore control portion associates each of saidone or more segments specified from said read-out write managementinformation with one or more new segments, and restores said one or moredata elements stored in said second storage device to the one or morenew segments.
 24. The storage control device according to claim 20,further comprising: a storage resource which stores said writemanagement information indicating which segment, among a plurality ofsegments, is allocated to said virtual volume; and a write controlportion which provides said virtual volume to said higher-level device,receives a write request for data for writing from said higher-leveldevice, selects one or more unallocated segments from among saidplurality of segments in response to the write request based on saidwrite management information, allocates the one or more selectedunallocated segments to said virtual volume, writes said data forwriting to the one or more allocated segments, and updates said writemanagement information to information indicating allocation of the oneor more segments to said virtual volume, and wherein each of saidplurality of segments is a storage area forming said one or more firststorage devices; said write management information is informationindicating which segment, among said plurality of segments, is allocatedto said virtual volume; and said restore control portion updates saidwrite management information stored in said storage resource toinformation indicating that no segments among said plurality of segmentsare allocated to said virtual volume, reads said one or more dataelements from said second storage device based on said read-out writemanagement information, selects and allocates to said virtual volumesegments for writing of read-out data elements from among said pluralityof segments, restores said read-out data elements to the allocatedsegments, and updates said write management information to informationindicating that the segments have been allocated to said virtual volume.